The sex-based distinctions of the Immigration and Nationality Act ('INA') have been remarkably resilient in the face of numerous equal protection challenges. In Miller v. Albright, Nguyen v. INS, and most recently United States v. Flores-Villar — collectively the "citizenship transmission cases"— the Supreme Court has upheld the constitutionality of the INA’s provisions that require unwed fathers, but not unwed mothers, to take a series of affirmative steps in order to transmit citizenship to their children born abroad.

The conventional account of these citizenship transmission cases is that the Court upholds sex-based distinctions that would otherwise fail heightened scrutiny because the immigration and citizenship context in which they arise typically affords plenary power to Congress. This Article argues that the conventional account is incomplete. The citizenship transmission cases are not best understood as examples of immigration law exceptionalism. To the contrary, they are remarkably consistent with the Court’s treatment of unwed fathers and mothers in its equal protection jurisprudence generally. An in-depth comparison of the citizenship transmission cases with the Court’s decisions regarding the rights of unwed fathers in a variety of other legal contexts reveals a uniform picture of how the Court approaches parental roles in the absence of a marital union — the Court assumes that the absence of legal ties with the father at the time of his child’s birth results in his real absence for purposes of establishing both paternity and a father-child relationship. The corollary to the unwed father’s absence is the unwed mother’s presence — the unwed mother is presumed throughout these decisions to remain with the child.

Underlying both the INA and the Court’s decisions endorsing the statute is therefore a consistent custody determination: the unwed mother, whether she is foreign or American, is understood to invariably retain custody over the child. This Article evaluates the potential consequences of making explicit the custody determination that is implicit in the Court’s citizenship transmission cases; uncovering the custody decision assumed by these rules, and assessing it on its own terms, provides reasons to question this recurring sex-based determination. This Article concludes by noting an important limitation of focusing on the gender-related aspects of the statute, namely the exclusion of any discussion concerning its citizenship-related repercussions.